Summary: Atherosclerosis is the primary cause of cardiovascular disease (CVD), one of the most critical causes of mortality in America. The current standard of care for at-risk patients involves dietary and lifestyle changes along with administration of statin drugs to lower blood cholesterol levels. However, a substantial residual risk of disease progression remains for patients treated with these conventional preventative and therapeutic options. Therapeutic strategies raising plasma high-density lipoprotein (HDL) levels failed to demonstrate reduced cardiovascular events in patients with coronary artery disease (CAD). Recent studies have provided insight into the possible mechanisms by which compositional alterations of HDL in patients with CAD leads to the functional heterogeneity. This continuous remodeling generates a heterogeneous population of circulating HDL, which can have distinct effects on endothelium. Due to the overwhelming number of HDL component combinations, the mechanisms of the altered effects on endothelial function remain poorly understood. Moreover, recent genetic studies suggest that bare measurements of plasma HDL levels are insufficient to accurately capture the functional variations caused by dynamic remodeling of HDL compositions. Furthermore, the inability of conventional experimental models to create a disease relevant state underscores the development of an in vitro model that reconstitutes pathophysiological conditions of vascular ECs in atherosclerosis. We propose to comprehensively investigate the endothelial effects of a wide-ranging library of engineered HDL-based nanoparticles (eHNPs) with representative functional proteins in pathophysiologically relevant microenvironments. We will create a novel in vitro surrogate model that replicates the structural and functional complexity of the human coronary artery and study the heterogeneous endothelial effects of various eHNPs for the treatment of atherosclerosis. We are particularly interested to determine if our approach uncovers new relationships between compositional and functional alteration of eHNPs, whether the heterogeneous endothelial effects of eHNPs are affected by disturbed flow in atherosclerosis, and whether ?healthy? eHNPs exhibit therapeutic potentials outperforming ?dysfunctional? eHNPs. This proposed work represents a risky expedition into new scientific territory in that it seeks to develop a new paradigm for studies on the functional heterogeneity of circulating HDL using innovative nanotechnology, microfluidics, and bioengineering approaches to develop an in vitro model of the human coronary artery. Therefore, the proposed work is uniquely suited to the New Innovator Award program rather than traditional grant mechanisms. The successful outcomes will provide a better understanding of the mechanisms leading to altered endothelial effects of HDL, improve the outcomes of the clinical studies by determining effects of alterations in the HDL proteome, and potentially lead to novel therapeutic measures capable of preventing the progression of atherosclerosis.